1. Technical Field
This invention relates to a holding structure for a touch panel, which is provided at a display or an operation unit of a variety of electronic devices and is used as an input device.
2. Description of the Related Art
Conventionally, electronic devices having a touch panel function as input means at the display surface have been widely used. One of the structures of the touch panels is a touch panel of a resistance-sensitive type. In the touch panel, usually ITO (indium oxide) film is formed in a predetermined pattern on the surface of the touch panel glass. Electrodes are connected to the end portion of the ITO film and the peripheral edge portions are coated by overcoating. And dot spacers are provided between the upper and lower panels both on which ITO films are deposited. When an operator presses the panel, the ITO films on the upper and lower panels get in contact with each other. The pressed position on the panel is detected in accordance with the resistance value at that time.
In the touch panel device, an operator carries out an input operation by directly touching such a display surface as a liquid crystal display panel. Even though the ITO films on the upper and the lower panels get in contact with each other when the operator presses the surface of the touch panel, the operator can neither feel nor be sure whether the contact is closed or not. And so, there is a touch panel equipped with so-called force feedback function which vibrates the touch panel by detecting the press operation and gives an operator an operation feeling.
As it is shown in Japanese Patent Application Publication No. 2006-227712 or in FIG. 4, the touch panel device equipped with the force feedback function is applied, for example, to handheld information equipment or the like. The device is composed of the liquid crystal panel 2 and the touch panel 4 being accommodated in a casing 6 made of resin or the like. The touch panel 4 is equipped with piezoelectric devices 3 for the force feedback function at the side edge portion. And elastic supporters 5 made of rubber or the like are disposed between the liquid crystal panel 2 and the touch panel 4 at four corners in the casing 6. The elastic supporters absorb the vibration of the touch panel 4 due to the piezoelectric devices 3 and hold the touch panel 4.
In the case of the touch panel device with the force feedback function and taking the structure disclosed in Japanese Patent Application Publication No. 2006-227712, an interspace is formed between the liquid crystal panel 2 and the touch panel 4 and the peripheral edges are open. Because of the openness, dusts are liable to come into the interspace between the liquid crystal panel 2 and the touch panel 4. And so, there is a touch panel device equipped with a protective sheet 7 which is applied to the outer front surface of the touch panel 4 covering the touch panel 4 and covering the opening portion 6a of the casing 6 as it is shown in FIG. 4. In the touch panel device taking the structure mentioned above, an operator can get a sure operation feeling because the piezoelectric devices 3 vibrates in accordance with the press operation of the touch panel 4. In addition, because the surface of the touch panel 4 is covered with the protective sheet 7, the dust-proof feature is high at the outer front surface side and the drip-proof feature can be given.
On the other hand, as it is shown in Japanese Patent Application Publication No. 09-115378, a structure which holds the liquid crystal panel fitting to a first elastic member of the frame and holds the touch panel with a second elastic member is proposed as a holding structure for a touch panel with high dust-proof feature and drip-proof feature. Furthermore, the second elastic member is integrally formed with a casing. In this way, the interspace between the liquid crystal panel and the touch panel is surrounded and sealed with the first elastic member, and the dust-proof feature of the interspace between the liquid crystal panel and the touch panel is designed.
In the case of the holding structure for a touch panel shown in FIG. 4 of the related art mentioned above, the dust-proof feature is effective against the dust coming from outside of the device. Since the interspace between the liquid crystal panel 2 and the touch panel 4 is supported only by the supporters 5 at the four corners, however, the interspace between the liquid crystal panel 2 and the touch panel 4 is open except the four corners and the dust is liable to attach to the front surface of the liquid crystal panel 2.
Furthermore, as it is disclosed in Japanese Patent Application Publication No. 09-115378, in the case that the liquid crystal panel takes a structure of being surrounded and held with the elastic member of the frame and being folded with a touch panel, the vibration of the touch panel of which an entire peripheral edge is tightly held with an elastic member of the frame is suppressed and the vibration is not liable to be effectively transmitted to the operator's fingers even though trying to apply the force feedback function to the touch panel.